Reprinted from the October 2016 AltTox Digest; used by permission.

Now that the human genome has been mapped, the next frontier is to map the human cellular phenotypes. An understanding of all the types of human cells and how they interact in the various tissues and organs will provide the new level of understanding of human biology needed to accomplish medical breakthroughs, understand physiological processes such as human development and aging, and understand pathophysiological processes such as disease and toxicity.

Cells are the basic building blocks of all human tissues and organs. Beginning in the embryo, cells divide and begin to specialize into the different cell types that make up the human body.

General estimates identify several hundred major cell types, however, new methods of characterizing cells show that even within what appears to be a homogenous population there is great variability.

The technique used to identify cells at the level of the single cell is single-cell messenger RNA sequencing (RNA-seq), where every messenger RNA species in a sample is sequenced and identified.  Credit: Genome Research Limited

The technique used to identify cells at the level of the single cell is single-cell messenger RNA sequencing (RNA-seq), where every messenger RNA species in a sample is sequenced and identified. Credit: Genome Research Limited

Recent government funding initiatives have spurred innovation and progress in studying cells at the level of the single cell. In 2014, the US National Institutes of Health (NIH) awarded $7.9 million to 25 projects studying various aspects of single cell analysis as part of the Single Cell Analysis Program (SCAP).

On October 13-14, 2016 an international group of renowned researchers met in London to discuss building the Human Cell Atlas. The Human Cell Atlas will be more than just a catalogue of static cell types. Like SCAP, it involves addressing the many challenges in characterizing human cell heterogeneity.

For more on single cell analysis and the new international effort to develop the Human Cell Atlas, see the entire article, “The Human Cell Atlas: An international effort,” on AltTox.org.